Generally, research into a secondary battery capable of being charged and discharged unlike a primary battery has been actively conducted in accordance with the development of state-of-the-art fields such as a digital camera, a cellular phone, a laptop computer, a hybrid vehicle, and the like. An example of the secondary battery includes a nickel-cadmium battery, a nickel-metal hydride battery, a nickel-hydrogen battery, and a lithium secondary battery.
Among them, the lithium secondary battery, which has an operating voltage of 3.6 V or more, is used as a power supply of a portable electronic device or a plurality of lithium secondary batteries are connected in series with each other to thereby be used for a high output hybrid vehicle. Since this lithium secondary battery has an operating voltage three times higher than that of the nickel-cadmium battery or the nickel-metal hydride battery and is more excellent in view of energy density characteristics per unit weight than the nickel-cadmium battery or the nickel-metal hydride battery, the use of the lithium secondary battery has rapidly increased.
Generally, the hybrid vehicle means a vehicle driven by efficiently combining two kinds or more of power sources with each other in a wide sense. However, in most cases, the hybrid vehicle means a vehicle obtaining driving force by an engine using fuel and an electric motor driven by power of a battery. This hybrid vehicle is called a hybrid electric vehicle (HEV).
In addition, the battery as described above may be applied to the next generation vehicle such as a plug-in hybrid electric vehicle (PHEV) and an electric vehicle (EV) as well as the HEV.
The next generation vehicle is necessarily mounted with a high voltage battery configured of the lithium secondary battery as shown in FIG. 1 in order to provide driving power of the electric motor. This battery supplies required power while being repeatedly charged/discharged during driving of the vehicle.
Generally, the high voltage battery provided in the next generation vehicle as described above has a very high voltage of about 680 V. Therefore, in the case in which the voltage of the battery is different from a potential of a vehicle body, it is difficult to maintain an electrically stable state, such that there is a risk that several problems may occur.
According to the related art, as a method of managing a voltage of a battery pack, a battery managing system that may be used in a vehicle using electric energy has been disclosed in Korean Patent Registration No. 10-0696673. However, a technology disclosed in Korean Patent Registration No. 10-0696673 is different from a technology of maintaining the potential of the vehicle body and the potential of the battery so as to be the same as each other.
Therefore, in the next generation vehicle, a technology of allowing a high voltage battery and a vehicle body to have equipotential is significantly required.